Friday, February 25, 2011

Soft Shackles, Stropes, and Square Riggers

Amsteel and other high-tech lines have made crazy things practical...

All-fiber standing rigging

Fiber lifelines

Safer jacklines

Fiber shackles

... except now that I think about it, none of this is completely new. It's where we started, when the first sailor decided to raise a few sticks and a woven mat above his raft to save paddling home. Clearly, we've improved on those early efforts. First, we used tarred steel, and then stainless steel. Heavier and more expensive, but durable and non-stretch with great abrasion resistance. But we couldn't leave it alone. I'm glad.

Traditional spliced strope with wall knot stopper

One of the biggest trends we've seen in the past 50 years is away from things that can be made to things that must be purchased. Given the steady decline in the basic shop skills of the average sailor and the increase in the complexity of our world, this trend is unstopable. But I try. Many of us try, and that is one of the great attractions of Amsteel; that a DIY sailor can replace purchased rigging services and create something better. I like that too.

Soft Shackles. A cool little invention: the only thing is the idea is about 200 years old on boats, and as old as ropes in general. Every pre-teen girl learned to tie these when braiding friendship bracelets. Every old salt learned to tie a strop with a splice and a turkshead; They are strong, cheap, and won't jam if loaded sharply. I've seen them used to arrest cannon. Rather similar, I think.

Still a good idea today. When made from Amsteel...

As strong as steel

Won't scratch the gel coat

Light

Cheap

Quiet

No tools required to install of remove

Colligo Marine style soft shackle above.Kolohov style shackle, below.

Not Difficult to make, just a diamond knot and a 12-strand splice, which has the nifty trait of sliding open and closed.

I learned of the old style strop from The New Glenans Sailing Manual over 20 years ago. There they were recommended as a means of attaching jib sheets on a dingy that was releasable and not likely to draw blood when changing a flogging sail. However, their method was simpler, taking only seconds to make, a minute if you're meticulous. The instructions, below, are for 1/8" line, but it will work in any size; I've made them up to 1/2" line, which will hold over 8,000 pounds (the line is doubled).

Cut and seal a 12-inch length of 1/8-inch line. This can be longer, much longer, if a longer strop is needed.

Double the line and tie an overhand loop near the bend, with the loop just large enough to pass a double overhand loop on doubled line without having to force it. Tighten by hand and with a fid in the loop.

Tie a double overhand loop near the end of the loop. Leave enough tail to help pull the knot through.

For frequent use the eye is easier to thread if the loop is spliced and thus the tail is only a single strand. Often I use only the cover or core of a line (single braid), as it is soft, super easy to splice, and generally free (throw-aways, from core or cover stripping). For example, my mainsail gaskets are spliced cover-only.

Notes: A double overhand works as well as on double braid as a diamond knot; it simpler and though smaller, presents a very sharp edge and thus is perhaps just as opening resistant as the latter which is more rounded. A turkshead works in 3-strand, where a tight double overhand is impossible. A single line works fine for longer stropes. Webbing is a mistake; depending on how the webbing lies, there may be no sharp edge on the knot. The loop can be spliced or seize, but that is just more complex; I use the bulk of the knot to advantage on tarps and awnings by tying the knots on either side of the grommet, keeping the strop captive and safe from loss. Strength loss in the knots is largely irrelevant, as the strope fails where the loop cuts the stopper knot.

Done. I've used them for 20 years to secure tarps and awnings on my boat. I've never had one shake loose. Larger per unit strength than Colloigo Marine-style soft shackles and considerably more bulky, they still come in handy due to shear ease and simplicity.

I've tested a number of these, in different materials, to failure; they never slip and always fail by the loop cutting the tail knot off, at about 160% of the single line strength... unless made of Spectra, whereupon the the stopper knot becomes undependable diamond knot more reliable. On single braid Amsteel a tuck splice is faster than a knot and thus we have the Kohlhoff type, which is easier to remove after loading.

To the right, a different style loop sewn from old 5/16 polyester.Broke at line strength.

Some applications, some for Amsteel shackles, some for polyester stropes:

Attaching tarps and awnings. No knots to jam and no chance of scratching the gelcoat. Any length you want.

Keeping a Cruising Boat for Peanuts--Available in PDF!

As much as I love sailing, putting my daughter through college and funding my 401K are more important. Transitioning from professional engineer to writer has transformed my habit of living efficiently into a passion for spreading funds thin. I like to think of it as a challenge for the imagination—it’s more fun that way.

I’ve written over 100 equipment reviews and engineering articles for popular sailing magazines, all based on laboratory and hands-on testing. I’ve spent 30 years learning how to maintain, fix, and upgrade. I've also spent 35 years as a chemical engineer, and my wife thinks I live in my basement shop.

As a result I’ve become a fair hand most crafts, never get stuck in the field with something I can’t fix, and I've learned to spread money thin, without compromising speed, reliability, or performance. Although I've written on many topics, my wife assures me this is the one I know best. My magnum opus?

About Me

This is my place to share my enthusiasm for the Chesapeake Bay, Delmarva Peninsula, PDQ And Corsair F-24 specific minutia, and sailing in general. As a regular contributor to sailing magazines including Practical Sailor and Good Old Boat (over 150 articles), it provides a place to try out ideas and publish the overflow. Here I can blurt it out half formed ideas, collect comments, and to see what questions my inquiry suggests. If I need to get long winded or philosophical, it’s my space to do so.
After 15 years of kayaking, 35 years of sailing, 35 years of rock and ice climbing, and 40 years as a chemical engineer, I still have much to learn and my life is still one giant science project. My end of the pier is always festooned with test rigs and warning signs. Every research project brings surprises—things I didn’t know, and just as often, things no one knew. And so through books and articles, I share.